Promoting CO2 absorption in aqueous amines with benzylamine

Post-combustion capture of CO2 is the most mature technique for reducing greenhouse gas emissions from coal fired power stations. In this study, aqueous benzylamine (BA) was investigated as a potential solvent for CO2 capture. First, CO2 loading capacities in 30% wt/wt aqueous benzylamine were determined by vapour liquid equilibrium (VLE) experiment in a stirred vessel between 40 °C and 80 °C, over a pressure range up to 900 kPa. At 15 kPa and 40 °C, 0.45 mol CO2/mol BA was absorbed. Protonation and carbamate thermodynamic equilibrium constants as well as the standard enthalpy of protonation were determined. Benzylamine showed a similar pKa (8.89 at 40 °C) but a larger pKa variation with temperature than MEA. The carbamate stability constant changed little with temperature. Benzylamine was then investigated as a CO2 absorption rate promoter in aqueous MDEA in a stirred vessel with a plane horizontal gas-liquid interface. Benzylamine performed better than MEA and DEA as a rate promoting agent, a larger amount of benzylamine in aqueous MDEA resulting in a higher enhancement of CO2 absorption rate.